The invention concerns copolymers from .alpha.-.beta.-unsaturated dicarboxylic acid esters with .alpha.-olefins, their production and their use as lubricants for the shaping treatment of plastics.
Olefin-maleic acid-copolymer derivatives are known from German Offenlegungsschrift DE-OS No. 27 27 239, which are constructed from olefins with an average of 2-24 carbon atoms and maleic acid and are esterified with univalent alcohols having a chain length from 2-20 carbon atoms in the mole ratio 1:0.5 up to 1:2 maleic acid to alcohol. The described olefin-maleic acid-copolymer derivatives are produced through copolymerization of maleic acid anhydride with .alpha.-olefins and connected esterification into semi- or diester. The there described olefin-maleic acid-copolymer derivatives are particularly suitable as lubricants for the shaping working-up of plastics.
Beyond that, high-molecular copolymers from .alpha.-olefins and .alpha.-.beta.-unsaturated dicarboxylic acid esters have been known for example as hair sprays (AU-PS No. 254,327) and as coating agents for medicines (AU-PS No. 263,011). These were produced by copolymerization of .alpha.-olefins and .alpha.-.beta.-unsaturated dicarboxylic acids or acid anhydrides and subsequent esterification of the copolymers.
German Offenlegungsschrift DE-OS No. 17 70 860 discloses a copolymerisate of a C.sub.22 -C.sub.28 -1-olefin and dibehenylmaleate, which was obtained by polymerization at 150.degree. C. It was suggested to add the product to hydrocarbons, in order to lower the solidification point or totally improve the flowability.
AU-PS No. 479,746 describes copolymerisate from .alpha.-.beta.-unsaturated dicarboxylic acid esters having one or two straight-chain ester groups with 18-44 C-atoms with C.sub.18 -C.sub.46 -.alpha.-olefins as flowability improver for wax-like hydrocarbon oil, the copolymerisate effecting a lowering of the pour point of the hydrocarbon oil.
Numerous substances have already been suggested as lubricants for the shaping working-up of plastics. With regard to their characteristics, they display more or less great differences, or possess in many respects advantages in contrast to others. One significant characteristic is the compatibility of lubricants with determined stabilizers, which are likewise mixed in for the deformation of plastics in order to avoid degradation phenomena resulting from the stress and strain occurring upon deformation. As stabilizers, for example metal salts or metalloorganic compounds are used. One known type of stabilizer, which is used for the stabilization of PVC (polyvinyl chloride), is composed from tin compounds. Many, even of these tin, stabilizers are not well compatible with lubricants. Those stabilizers for which this applies in particular measure include, for example, dibutyl tin-di-monomethylmaleate. In order to be able to produce mixtures with lubricants, both stable and of good dosability, also with these stabilizers, which are very approved in practice, efforts have for a long time been made--without great success--to test lubricants which would make such mixtures possible.